Bonding Jumper Size

[Will Wire]

I recently did a service change on a ranch to include an additional house. It is a 120/240 single phase service. The service conductors entering the gutter from the service drop are three copper 500 KCmil. I have three disconnects tapped off these conductors. A 50 amp for a well, a 150 amp for one house, and a 200 amp for another house.
What size bonding jumper do I need to bond the gutter to the three disconnects? If I understand it correctly, 250.102 (C)(1) refers me to Table 250.66 for a bonding jumper size of 1/0 based on the 500 KCmil ungrounded service conductor. Do I understand this correctly? Thanks

 

[Smart $]

I didn't check size, but your premise is correct regarding section and table. The only thing I see as a potential issue is you may be installing a larger than required jumper. If you actually tapped the 500's with a smaller conductor, you'd base the jumper size on the tap conductor size.

 

[augie47]

From the wording, I find this interesting.... and the answers may vary.
I can see a number of approaches.
As both you and Smart$ stated, 250.66 is the guide.
IF your disconnects are fed from the wireway by metallic conduits you might accomplish your grounding simply buy using bonding locknuts on those nipples.
Most commonly here, the wireway would be bonded from the service neutral in the wireway with a 1/0 connected to the neutral in the wirweway.
The method you suggested, bonding from the disconnects back to the wireway would be the least used here and sizing those three jumpers would be the controversial part. Since the 500s require a 1/0, and your neutral conductors to one or more of the disconnects may be less than 1/0.

 

[david]

Since 500 Kcmil copper service conductors enter the gutter you bond the gutter based on 500 Kcmill conductors. I agree with a 1/0 bonding conductor based on 250.66

Since you said it is on a ranch, most ranches would have agricultural building involved in the service distribution system. I am making the assumption this is a distribution point and there may be additional requirements or conditions in article 547 depending on where the feeder disconnects are located and the buildings involved for the premise distribution system.